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Buffer pool vs database pages

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  • Buffer pool vs database pages

    Hi

    How is it possible that the "Database pages" are higher than the actual buffer pool size ?


    Mysql Percona Server version 5.5.23-55-log
    Buffer pool size 639999
    Database pages 845454

    Isn't it so that data pages represent the amount of pages in the buffer pool ?
    I also see that the server is using more memory than I have set it up to use in my.cnf

    Can this have something to do with using row format compressed ?
    I see this raise in db pages if someone does a really huge dataset fetch from a table with many rows.

    From the innodb status:
    ----------------------
    BUFFER POOL AND MEMORY
    ----------------------
    Total memory allocated 10772480000; in additional pool allocated 0
    Internal hash tables (constant factor + variable factor)
    Adaptive hash index 302005952 (166014536 + 135991416)
    Page hash 10376728 (buffer pool 0 only)
    Dictionary cache 85223713 (41505008 + 43718705)
    File system 1374512 (82672 + 1291840)
    Lock system 25941208 (25940456 + 752)
    Recovery system 0 (0 + 0)
    Dictionary memory allocated 43718705
    Buffer pool size 639999
    Buffer pool size, bytes 10485743616
    Free buffers 0
    Database pages 845454
    Old database pages 312071
    Modified db pages 165
    Pending reads 0
    Pending writes: LRU 0, flush list 0, single page 0
    Pages made young 877727, not young 0
    2.31 youngs/s, 0.00 non-youngs/s
    Pages read 1118257, created 63316, written 1376455
    0.10 reads/s, 0.03 creates/s, 22.78 writes/s
    Buffer pool hit rate 1000 / 1000, young-making rate 3 / 1000 not 0 / 1000
    Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
    LRU len: 845454, unzip_LRU len: 93501
    I/O sum[4]:cur[0], unzip sum[85]:cur[0]

  • #2
    Buffer pool size is the size in megabytes, the other number indicates the nuber of pages (each is standard 16 kB).

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    • #3
      No that is not correct, this is buffer pool in pages:
      Buffer pool size 639999
      Database pages 845454

      And this is bytes:
      Buffer pool size 639999 x 16k = 10485743616
      Buffer pool size, bytes 10485743616

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